WASHINGTON – Democrats’ renewed focus on bolstering the economy faces a key test today, with the Senate expected to hold a procedural vote on what Majority Leader Harry Reid, D-Nev., hopes will be the first of several job-creation bills.

The chamber will vote on whether to proceed with a $15 billion measure that includes a one-year Social Security tax break for companies hiring new employees who have been out of work for at least 60 days. The package also would reauthorize the Highway Trust Fund, allow companies to write off equipment purchases, and expand Build America Bonds, which help state and local governments fund infrastructure projects.

But the measure does not include a host of other provisions from an $85 billion bipartisan package negotiated by Sens. Max Baucus, D-Mont., and Charles Grassley, R-Iowa. Reid’s decision to discard that bill in favor of a smaller version has cost him the public support of several Republicans, casting doubt on whether Democrats will garner the 60 votes necessary to proceed Monday.

”We’re pretty close,” Reid said Friday during a television appearance in Nevada, adding that he thought ”fat cats” would have benefited too much from the larger Baucus-Grassley bill.

As of Sunday, no Republicans had declared intentions to vote to proceed on the slimmer bill. Under normal circumstances, Democrats would need at least one GOP vote to reach a filibuster-proof majority. With Sen. Frank Lautenberg, D-N.J., absent after receiving a diagnosis of cancer last week, his party will need to lure at least two Republicans on Monday in order to set up a vote on final passage later this week.

Minority Leader Mitch McConnell, R-Ky., said on ”Fox News Sunday” that Republicans ”may well” support the jobs bill, though that doesn’t necessarily mean the GOP will help Democrats in today’s procedural vote.

”What was a mystery to us is how the bipartisan bill got shelved,” McConnell said. ”Many of my members were going to support it. And all of a sudden the majority leader decided to skinny it down.”

Sen. Orrin Hatch, R-Utah, co-author of the Social Security tax credit at the heart of the measure, has declared publicly that he will not vote to proceed today. Sen. Susan Collins, R-Maine, a key moderate, sent Reid a letter on Friday imploring him to ”reconsider your decision and proceed to the jobs bill” negotiated by Baucus and Grassley.

Beyond the usual handful of GOP centrists such as Collins, Democrats are also targeting newly elected Sen. Scott Brown, R-Mass., hoping to persuade him to vote for the bill or paint him as a lockstep conservative if he doesn’t.

”The question for Scott Brown and others is whether they’re going to vote the way their constituents want, or based on the demands placed on them by their leadership,” said Reid spokesman Jim Manley.

Brown has allowed that there are some ”good parts” to Reid’s jobs bill, but his office declined to comment on his intentions Sunday.

Republicans’ complaints about Reid’s bill are less about the substance of the measure than the process that created it. ”This is not how you legislate in the United States Senate and demonstrates a tremendous arrogance of power,” Hatch said.

Democrats say that Republicans should vote on the bill’s merits, and that they shouldn’t count on a return to the full Baucus-Grassley bill — which includes $31 billion worth of tax-break extensions sought by Republicans — if today’s vote fails.